1. Field of the Invention
The present invention generally relates to a method for enhancing the rate of the formation of the reaction product of a carboxylic acid and a urea, such as a substituted urea, via acid addition. The reaction product may be used as an agricultural product to improve plant growth. More specifically, the present invention is directed to the addition of at least one acid to a solution including the carboxylic acid and urea.
2. Description of the Background
Urea, being approximately 46% by weight nitrogen, has long been preferred as a nitrogen source for fertilizing soils to stimulate plant growth. However, urea suffers from high ammonia losses when used in the presence of moisture. This disadvantage effectively restricted the use of urea for many years. It is believed that these losses are caused by the hydrolysis of urea in the presence of moisture and the enzyme urease. The addition of a water soluble salt to aqueous solutions of urea has been suggested as a means for reducing ammonia volatilization. See U.S. Pat. No. 4,500,335. While substituted ureas are also known, e.g., diphenylurea, they have found little agricultural use.
Diacyl ureas are a product formed by the reaction of a carboxylic acid and a urea. For example, diformylurea (DFU) is formed by the reaction of 2 equivalent of formic acid with urea over 5-7 days. The by-product of the reaction is water.
While activity with this formulation has been good, improvements in performance are desirable. As such, previous formulations have included the addition of various compounds to the diacyl urea formulation prior to use. For example, potassium hydroxide and formate may be added to the formulation. The addition of potassium hydroxide may be included to adjust the pH of the formulation, see U.S. Pat. No. 6,710,085, U.S. Pat. No. 6,448,440, and U.S. Pat. No. 6,040,273, the contents of which are expressly incorporated herein by reference. However, a formulation that does not require the addition of such compounds would be advantageous.